Gold mining is arguably the world’s dirtiest and most polluting industry. Cyanide heap leaching is the cheapest way of extracting gold and is commonly used (90% of gold is extracted this way). This process takes large amounts of cyanide and leaves behind toxic materials. Cyanide is harmful to both humans and animals, one teaspoon of 2% cyanide will kill a human being. Cyanide waste is stored in reservoirs and spills from these lakes have made their way into water systems with consequences for the environment, wildlife and local communities. Gold mining has polluted water all over the world with dangerous chemicals such as arsenic, cyanide, lead and mercury. Some mines regularly dispose of their waste in lakes, rivers and oceans and in developing countries waste is often dumped. Modern mining techniques that use vast amounts of fresh water are just as damaging to bodies of water as older techniques that pollute it. Long term effects include acid mine drainage (raises acid levels in water), poisoned drinking water and harm to wildlife populations.